1. Field of the Invention
The present invention relates to an image forming apparatus that can be embodied in relation to, for example, a light emitting diode (abbreviated as LED) head, a thermal head or the like.
2. Description of the Prior Art
It is known in prior art to provide a light emitting diode head comprising a pluraltiy of arrays each formed from a plurality of light emitting diodes arranged in a row, one terminal of each of the printing elements disposed symmetrically to each other in adjacent arrays being connected to an individual signal line in such a manner as to arrange the individual signal line in a zigzag pattern, the other terminal of each of the thus disposed light emitting diodes being connected to a common signal line provided for each array, thus forming a so-called dynamic drive matrix wiring pattern. At one end of the row of arrays, there is disposed a driving means which sequentially selects the common signal lines in the sequence of arrays and sequentially supplies power to the light emitting diodes contained in the selected array via the individual signal lines. The driving means selectively drives the light emitting diodes, as described above, with printing data to be recorded and individually corresponding to the light emitting diodes being given in the direction in which the light emitting diodes are arranged, i.e. from one end toward the other end of the array.
Such prior art is disclosed, for example, in U.S. Pat. No. 3,740,570, U.S. Pat. No. 3,517,258, and Japan Patent Publication No. 1-20751.
The above prior art requires that the printing data sequentially given to the printing elements along the arranged direction thereof be supplied to the individual signal lines with its sequence alternately reversed each time the data is transferred to each array; otherwise, the printing elements cannot be driven in sequence along the arranged direction thereof in accordance with the image data. The driving means temporarily stores the supplied image data in memory in order to transfer and sort the image data for each array, the data thus stored in memory being addressed in the forward or reverse direction to place them on the respective individual signal lines.
Therefore, the prior art requires the provision of a memory for the transfer and sorting of printing data for each array, which not only makes the construction complex and expensive but also requires a relatively long time for storing and sorting the printing data, thus imposing a limit to increasing the printing speed.